2.8 Rigid Body settings and how to use?
I just tried something similar and it worked OK, I'm guessing your spheres are too close / touching on the initial frame. This will upset things.
Here's my result-
https://www.dropbox.com/s/cdtnwukjwakg6kc/RigidSpheres.mp4?dl=0

And here's the scene-
https://www.dropbox.com/s/aw6pmq5tmis0kee/RigidSpheres.blend?dl=0

If you move my spheres so they're touching/intersecting they repel each other as they start to fall.

Cheers
Mark